The present invention relates to drywall construction and, more particularly, to an improved back blocking device for providing a smooth flat finished butt joint.
In the construction of buildings, interior walls and ceilings typically consist of a layer of gypsum wallboard attached to construction beams made of wood or other materials. The joining of adjacent edges of two pieces of wallboard is accomplished by the application of a plaster-like material to the joint with an embedded layer of paper tape to inhibit cracking of the finished joint. Usually the longer edges of the wallboard are pre-beveled to receive the plaster so that the finished joint is flat and smooth. The ends of the wallboard, however, are not beveled. Additionally, when it is necessary to cut a portion of the wallboard away when fitting it into a smaller space, the pre-beveled edges are frequently removed. In such cases, the finished joint necessarily bulges out of the plane of the wall and is unsightly. An example of such a structure is illustrated in FIG. 1 where the nonbeveled two adjacent edges of two pieces of wallboard 10 and 12 are positioned in alignment with the center of a wooden construction beam 14 and nailed in place with nails 16. Several layers of plaster 18 and an embedded layer of paper tape 20 are applied to the area to form the butt joint. The plaster leaves a bulge 22 that extends away from the plane 24 of the wallboard, as shown. The plaster is feathered outwardly on either side of the joint for about 24 to 36 inches to render the bulge less obvious. This requires a substantial amount of skill and experience and, more importantly, the finished joint is unsightly. This is especially apparent when a glossy finish is applied to the finished surface.
In an effort to overcome this problem, the edges of the two pieces of wallboard to be joined are positioned between two adjacent construction beams. Joint support devices that extend from one construction beam to the other are positioned at intervals along the butt joint and are spaced slightly away from the surface of the wallboard so that when the edges of the wallboard are attached to the support devices, the edges are pulled toward the support device and out of the plane of the wallboard. This provides a recessed area along the joint for receiving the plaster material in a manner similar to that of pre-beveled edges. Examples of such joint support devices are disclosed in U.S. Pat. No. 4,237,669 that issued Dec. 9, 1980 to Hunter and U.S. Pat. No. 4,392,336 that issued Jul. 12, 1983 to Ganssle. Both of these devices have metal structures that extend from one construction beam to the other and are attached to the outwardly facing edges of the beams so that when the wallboard is installed, portions of the support devices are necessarily sandwiched between the mounting surfaces of the beams and the surfaces of the wallboard. These devices cause several problems. First, once the wallboard is held in place preparatory to nailing to the construction beams, the joint support devices are no longer visible, and since they are made of metal, they may interfere when nailing the wallboard to the beams. Further, the portion of the metal structures that are sandwiched between the mounting surfaces of the beams and the wallboard cause bulges in the wallboard and can damage the inner surface of the wallboard if, when nailing, a hammer blow inadvertently strikes the wallboard near an edge of the metal.
Another problem associated with both of these devices is that they are spaced apart a substantial amount so that the two edges of the wallboard are not supported along their entire lengths. This causes the edges of the wallboard to scallop by bowing outwardly in the spaces between the supports, making it more difficult to apply the plaster material and obtain a smooth, flat butt joint. While it is good practice in the industry to glue these butt joint edges to the construction beam for the entire length of the butt joint, this cannot be done in this case. Further, because the joint support devices are made of metal, prior to attaching the edges of the wallboard to the support device, suitable holes must be drilled through the metal to receive the wallboard mounting screws, or self drilling and tapping screws must be used. This, of course, adds to the cost of producing the joint.
Another example of a joint support device is disclosed in French Patent No. 1,287,947. Here, cleats are positioned between two adjacent construction beams and nailed in place. The cleats are spaced part along the site of the butt joint with their wallboard mounting surfaces spaced a slight distance from the wallboard. The two edges of the two pieces of wallboard are then nailed to the cleats causing the edges to bend slightly inwardly out of the plane of the wallboard. Since the cleats are spaced apart a substantial amount so that the two edges of the wallboard are not supported along their entire lengths, as set forth above, the edges of the wallboard will scallop by bowing outwardly in the spaces between the supports, making it more difficult to apply the plaster material and obtain a smooth, flat butt joint. Again, there is no way to glue the edges of the butt joints along their entire lengths. Additionally, the cleats must be accurately cut to fit between the two construction beams, accurately spaced from the wallboard mounting surface, and then securely nailed to the beams, generally requiring the services of a carpenter. This additional work, of course, increases the cost of making the butt joint.
U.S. Pat. No. 5,832,684 issued on Nov. 10, 1998 to Trout et al. discloses a butt joint support device that is easily installed, by the wallboard installer, between two construction beams without cutting to size and which does not require attachment to the beams in any way. The device does not interfere with the normal attachment of the wallboard to the construction beams and provides support to the edges of the two pieces of wallboard. The device has a wallboard mounting surface that is spaced a desired distance from the wallboard to provide the desired beveled effect and requires no drilling of holes during installation of the wallboard. This device, however, is limited in that a completed device can only provide one desired beveled effect. If a beveled effect of a greater angle or smaller angle is desired, the wallboard installer would need to use a separate device manufactured to specifically create the desired beveled effect. Because different types of installation require different beveled effects, more devices are required to be manufactured and stocked. This is both expensive and uneconomical.
It is therefore desirable to develop a rigid back blocking device configured in such a way that it can create more than one beveled effect. A versatile design would decrease manufacturing and storage costs and accommodate varying need.
This invention relates to a device for use between two construction beams for connecting adjacent ends of a first and second piece of wallboard to form a butt joint. The device comprises an elongated member having a longitudinal axis, a first side and a second side. The first side having a first offset of a first distance. The second side having a second offset opposed to the first offset of a second distance. First and second pieces of wallboard are positioned on either the first side or the second side of the elongated member and converge for attachment to the first or second side of the elongated member substantially near the longitudinal axis to form a butt joint. The elongated member, therefore, can be installed using either the first side or the second side to create a beveled effect of a desired thickness to accommodate varying need.